Instructional Coaching is one model of CPD, others are available! Because schools are complex organisations, it's impossible to advocate one model in totality, and it's probable that schools should blend models. For example, at our school we

Start with rapid knowledge growth through traditional INSET style CPD and/or using Carousel Teaching

Follow up with lots and lots of observations and learning walks

Make decisions about what to do next based on findings. If new strategies are implemented well, we move on. If not, we reflect and figure out a different path

Individual colleagues who need more support might have more targeted interventions, that often has characteristics typical of Instructional Coaching (though we don't use the term)

We also have elective CPD, so people can choose a thing to focus on more that year, and we put on specific session on a range of topics that people can choose from.

So essentially we have a "whole school this is what we do" track, and an elective "this is what I want to work on this year" track.